This invention relates to a wiring harness for an air intake manifold including a flexible circuit sandwiched between layers of foam attached to the intake manifold.
Typically an air intake manifold includes a plurality of sensors and actuators for monitoring and controlling a motor vehicle engine. A wiring harness having a plurality of multi-strand wires provides for electrical communication between the sensors, actuators and an engine controller. Typically wiring harnesses are fabricated by crimping terminals onto multi-stranded wires, then hand assembling the terminals into a plastic connector. Wiring harnesses fabricated in this manner are unreliable because of the possibility that an errant strand of wire that was not crimped may cause a circuit disabling short. More problematic is the errant strand of wire that may cause an intermittent short that are difficult and time consuming to diagnose and correct. Another problem inherent in typical wiring harnesses derives from the random bundling of the wires. Random bundling of wires may cause electromagnetic or radio frequency interference between wires in the bundle. The interference will be difficult to detect and can cause the degradation of sensor and actuator function.
Recently intake manifolds are being fabricated from plastic. Plastic manifolds have challenges relating to noise properties. Typically, a layer of foam covering the plastic intake manifold is thus used to dampen noise. The layer of foam will either include a plurality of cut outs to accommodate mounting of the plurality of sensors and actuators, or a single uniform layer of foam covering both the intake manifold and the plurality of sensors and actuators.
Current wiring harnesses are deficient because they require many expensive and unreliable hand operations that may result in intermittent electrical problems that are difficult to diagnose and correct. Further, intermittent electrical problems may cause repeated trips to a repair facility causing increasing customer dissatisfaction. For these reasons, it is desirable to provide a wiring harness that can be integrated with the layers of noise reducing foam to provide noise abatement, ease assembly and reduce occurrences of intermittent electrical shorts.
The subject invention is a wiring harness for an intake manifold mounted to an internal combustion engine including a flexible circuit assembly included within foam attached to the top of the intake manifold. The flexible circuit assembly replaces the plurality of multi-stranded wires included in a typical wiring harness. The flexible circuit assembly of the subject invention offer benefits over prior art wiring harnesses by reducing weight, lowering manufacturing costs, improving reliability, and simplifying problem diagnosis and repair. Further, because the flexible circuit assembly is comprised of a plurality of individual printed circuits arranged in a predetermined pattern; the amount of electromagnetic and radio frequency interference can be predicted and corrected during design of the flexible circuit assembly.
In an additional embodiment of the subject invention, the sensors and actuators are part of the circuit assembly. Integrating the sensors and actuators with the circuit assembly provides for ease of assembly and repair. The ease of repair is attained by providing for replacement of all the electrical components along with the circuit assembly instead of requiring a maintenance technician to track an electrical problem to one of the multiple wires, actuators or sensors. Replacement of the circuit assembly, sensors and actuators as a single unit reduces the amount of time required to correct an electrical problem and prevents multiple trips to a repair facility caused by miss-diagnosis of the electrical problem.
Most preferably the flexible circuit is sandwiched between foam layers, although it could also be molded into a single foam layer.
The subject invention overcomes the deficiencies of prior art multi-strand, multi-wire wiring harness by providing a flexible circuit assembly that reduces weight, eases assembly and reduces the time required to diagnose and correct electrical problems.